PowerShell Start-Process cmdlet when ArgumentList is empty

Question

I've simplified my situation as much as possible. I have a PowerShell script that programmatically starts a process with the "Run as administrator" option using the Start-Process cmdlet:

param
(
    # Arguments to pass to the process, if any
    [string[]] $ArgList
)

if($ArgList)
{
    Start-Process -FilePath notepad.exe -ArgumentList $ArgList -Verb RunAs
}
else
{
    Start-Process -FilePath notepad.exe -Verb RunAs
}

Since ArgumentList cannot be NULL nor empty, I had to add the if-else to avoid a ParameterArgumentValidationError error.

Everything works as expected with no problem, but I was just wondering if there's a more elegant (but still simple) way to accomplish that without using the if-else blocks.

score 6 · Answer 1 · edited Jul 02 '15 at 13:03

6

You can use the "splat" operator to dynamically add parameters.

Define a hash with keys for parameter names. And then pass that to the cmdlet:

$extras = @{}
if (condition) { $extras["ArgumentList"] = whatever }

Start-Process -FilePath = "notepad.exe" @extras

edited Jul 02 '15 at 13:03

Matt

45,022
8
78
119

answered Jul 02 '15 at 12:22

Richard

106,783
21
203
265

1

Thank you, I didn't know the splat operator. That's not complicated at all but I think the original code is more readable so I'll probably keep my _if-else_ blocks. Answer upvoted though. – mguassa Jul 10 '15 at 12:09
@mguassa Your solution might look cleaner, but it is NOT a good idea in general, as it involves duplication of code and maintaining duplicate pieces of code. This answer - is the right way to do it. – Alek May 10 '20 at 06:35

score 0 · Accepted Answer · answered Jul 02 '15 at 12:26

0

There is a way using the splat operator @ (see Richard answerd) and maybe using a format string with a condition. However, I think the If-else Statement is the most readable and clear way to do this and I wouldn't try to simplify it.

answered Jul 02 '15 at 12:26

Martin Brandl

56,134
13
133
172

1

I agree, it's good to know about the solution with the splat operator, but the original code looks more readable and it's probably what I'm going to use. – mguassa Jul 10 '15 at 12:13
Well, I also miss something like a '$variable ? then : else' statement. – Martin Brandl Jul 10 '15 at 12:15
That would be cool, but I don't think PowerShell supports the ternary operator – mguassa Jul 10 '15 at 13:28
FYI [Ternary operator in PowerShell](http://stackoverflow.com/questions/31341998/ternary-operator-in-powershell) – mguassa Jul 11 '15 at 07:38
3

When more than one argument must be manipulated this way (through if..else.. structures) the splat operator becomes very handy! :) – Zoltan Hernyak May 29 '18 at 11:58
@ZoltanHernyak true! – Martin Brandl May 29 '18 at 11:59

score 0 · Answer 3 · answered Dec 07 '22 at 14:46

I am using Powershell 7 and do not have this problem, I run Start-Process -ArgumentList $args in a function where $args is sometimes null and it works fine.

However, my script does not run on Windows PowerShell.

It looks like Powershell 7 no longer requires you to have the if-else statement here.

PowerShell Start-Process cmdlet when ArgumentList is empty

3 Answers3